package com.haozhiyan.zhijian.widget;

import android.graphics.Rect;
import android.support.v7.widget.RecyclerView;
import android.view.View;

/**
 * Create by WangZhenKai at 2019/4/24
 * GridLayoutManager或者StaggeredGridLayoutManager 设置Item间距的办法
 */
public class GridSpacingItemDecoration extends RecyclerView.ItemDecoration {

    //列数
    private int spanCount;
    //间隔
    private int spacing;
    //是否包含边缘
    private boolean includeEdge;

    public GridSpacingItemDecoration(int spanCount, int spacing, boolean includeEdge) {
        this.spanCount = spanCount;
        this.spacing = spacing;
        this.includeEdge = includeEdge;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        //这里是关键，需要根据你有几列来判断
        int position = parent.getChildAdapterPosition(view);
        //item position
        int column = position % spanCount;
        // item column
        if (includeEdge) {
            outRect.left = spacing - column * spacing / spanCount;//spacing - column * ((1f / spanCount) * spacing)
            outRect.right = (column + 1) * spacing / spanCount;//(column + 1) * ((1f / spanCount) * spacing)

            if (position < spanCount) {
                // top edge
                outRect.top = spacing;
            }
            outRect.bottom = spacing;
            // item bottom
        } else {
            outRect.left = column * spacing / spanCount;//column * ((1f / spanCount) * spacing)
            outRect.right = spacing - (column + 1) * spacing / spanCount;//spacing - (column + 1) * ((1f / spanCount) * spacing)
            if (position >= spanCount) {
                outRect.top = spacing;// item top
            }
        }

    }
}
